The present invention is directed to overcoming problems associated with collapsible three-dimensional viewers called stereoscopes. Three-dimensional viewing of photographs generally is achieved by having an observer view one image with the left eye, and another similar image with the right eye. These two images are different views of the same object(s) and are placed adjacent to each other forming what is called a stereogram. Often times, the two images on the stereogram are photographs of an object taken by a camera from two slightly different angles. When the left eye sees the left image and the right eyes sees the right image on the stereogram, the observer's brain interprets the two different images as a single composite image that appears three-dimensional. Collapsible stereoscopes come in various sizes and shapes and are useful in that they are light weight, portable, and can be mailed in thin envelopes.
Many collapsible stereoscopes are box shaped, and constructed from a single cardboard blank having flaps, wings, or protruding edges that can be configured together to form an assembled stereoscope. It is important that when the stereoscope is assembled, it remains in a fairly rigid formation because the distance from the stereogram to the observer's eyes is critical for the brain to interpret two two-dimensional images as a single three-dimensional image. Creating a stereoscope that is both easily collapsible but also rigid enough to keep images in a stable location when assembled has been difficult. It has also been a challenge to make collapsible stereoscopes that have enough light to illuminate the stereogram, but also reduce or prevent shadowing on the stereogram caused by light that enters from the side of the stereoscope. Furthermore, it has been difficult to create a stereoscope having an easy assembly but also has the capability of easily interchanging stereograms inside of the stereoscope.
There are several types of collapsible stereoscopes with different features. Some stereoscopes lack the structural support of having side walls, including: U.S. Pat. No. 712,410 to Reichenbach, U.S. Pat. No. 962,643 to Knopping, U.S. Pat. No. 2,018,739 to Pauchek, U.S. Pat. No. 1,097,601 to Maerz, U.S. Pat. No. 2,283,777 to Wendling, U.S. Pat. No. 2,757,573 to Turner, U.S. Pat. No. 2,984,153 to Brennan, and U.S. Pat. No. 5,002,363 to Tanaka. Other stereoscopes are formed from several separate pieces of unconnected material that must be joined together, or have no mechanism that keeps the stereogram in place, including: U.S. Pat. No. 2,368,480 to McClure, U.S. Pat. No. 5,309,281 to Rover, and U.S. Pat. No. 6,151,165 to Tomita. Other stereoscopes have side wall supports but would likely cause shadowing on the stereogram, or exclude outside light altogether, such as U.S. Pat. No. 2,616,333 to Tinker, U.S. Pat. No. 2,662,442 to Gowland, U.S. Pat. No. 2,789,460 to Kaufman, U.S. Pat. No. 2,821,884 to Austin, and U.S. Pat. No. 6,069,735 to Murphy. Others, because of a closed-box assembled configuration, would make it difficult for the user to interchange stereograms in the stereoscope, such as the one described in U.S. Pat. No. 3,734,596 to Nerlich.
Therefore, there is a need for improved collapsible stereoscopes that are sturdy, easy to assemble, brace the stereogram, and reduce or prevent shadowing on the stereogram.